Method for the preparation of shaped article of crosslinked poly (vinylidene fluoride)

Abstract

Shaped articles of a crosslinked poly(vinylidene fluoride) resin can be prepared in a relatively simple process to be imparted with greatly improved resistance against heat, water, and chemicals in a much higher productivity than in the conventional electron-beam irradiation method. The method comprises the steps of (a) compounding the resin with an organosilane compound having an ethylenically unsaturated group, e.g., vinyl, and at least one alkoxy group in a molecule and a free-radical generator, e.g., organic peroxides, (b) heating the resin compound to effect graft-polymerization of the organosilane compound to the polymer molecules, (c) shaping the resin compound into a desired form, and (d) heating the shaped body in water containing a silanol-condensation catalyst dissolved or dispersed therein.

What is claimed is: 
     
       1. A method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin which comprises the steps of: (a) compounding a poly(vinylidene fluoride) resin with an organosilane compound represented by the general formula   R.sup.1.sub.4-n SiR.sup.2.sub.n,     in which R 1  is an ethylenically unsaturated group, R 2  is an alkoxy group or an alkoxy-substituted alkoxy group and the subscript n is 1, 2 or 3, and a free-radical generator to give a resin compound;     (b) heating the resin compound to effect graft-polymerization of the organosilane compound on to the molecules of the poly(vinylidene fluoride) resin;   (c) shaping the resin compound into a form of an article; and   (d) heating the thus shaped article in the presence of water and a silanol-condensation catalyst in contact therewith.   
     
     
       2. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the organosilane compound is selected from the class consisting of vinyl tri(β-methoxyethoxy) silane, vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tri-n-propoxy silane, vinyl tri-n-pentoxy silane, divinyl di(β-methoxyethoxy) silane, divinyl dimethoxy silane, divinyl diethoxy silane, divinyl di-n-propoxy silane, divinyl di(isopropoxy) silane, divinyl di-n-pentoxy silane, trivinyl methoxy silane, trivinyl n-pentoxy silane, trivinyl β-methoxyethoxy silane, 3-acryloxypropyl trimethoxy silane and 3-methacryloxypropyl trimethoxy silane. 
     
     
       3. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 2 wherein the organosilane compound is vinyl tri(β-methoxyethoxy) silane. 
     
     
       4. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the amount of the organosilane compound is in the range from 1 to 30% by weight based on the poly(vinylidene fluoride) resin. 
     
     
       5. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the free-radical generator is an organic peroxide. 
     
     
       6. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 5 wherein the organic peroxide is selected from the class consisting of 1,3 bis(tert-butylperoxy isopropyl) benzene, dicumyl peroxide and dibutyl peroxide 
     
     
       7. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 6 wherein the organic peroxide is 1,3-bis(tert-butylperoxy isopropyl) benzene. 
     
     
       8. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the silanol-condensation catalyst is dibutyl tin dilaurate. 
     
     
       9. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein heating of the resin compound in step (b) is performed at a temperature in the range from 170° to 220 ° C. for a length of time in the range from 1 to 60 minutes. 
     
     
       10. The method for the preparation of a shaped artIcle of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the amount of the free-radical generator is in the range from 0.1 to 20% by weight based on the amount of the poly(vinylidene fluoride) resin. 
     
     
       11. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the shaped article is heated in step (d) in water containing the silanol-condensation catalyst dissolved or dispersed therein. 
     
     
       12. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 1 wherein the content of the silanol-condensation catalyst in water is in the range from 1 to 20% by weight. 
     
     
       13. The method for the preparation of a shaped article of a crosslinked poly(vinylidene fluoride) resin as claimed in claim 12 wherein the shaped article is heated in step (d) at a temperature in the range from 60° to 100° C. for a length of time in the range from 5 to 48 hours.